The present invention relates to an image forming apparatus such as a complex-type digital copier for reading a document image, reproducing the image on paper, and printing image data supplied from a personal computer or the like through the LAN on paper.
Recently, a digital copier that accepts in advance the contents to be reproduced or printed out as jobs and executes the process for every unit, are practically in use.
In addition, the digital copier comprising a sorter (finisher) for providing the stapling process by a stapler are also practically in use.
When the job where sheets of paper having different sizes such as A3, A4 and the like are mixed, the operation can be executed in the only digital copier of the completion type.
The completion type indicates the operation of accepting and registering all the image data that is to be processed as the job and then start the printing.
Further, as for the number of maximum sheets of paper that can be stapled for each copy, different values are determined in accordance with the size of the paper, by the limitation of the finisher. For the same reason, the stapling process is also prohibited when the sheets of paper having different sizes are mixed.
Thus, the maximum number of sheets of paper that can be stapled is set in every size of the paper. Therefore, in a case where the number of sheets exceeds the set value, even if the execution of the stapling process is set, the process has to be canceled. In addition, in the case of the size-mixing job, the stapling process also has to be canceled.
That is, when the operation is executed in the digital copier of the completion type in which the outputting is started after inputting the image data has been finished, the number of sheets of the input document and the size-mixing job are known in advance when the inputting has been finished, i.e. before the outputting is started, as explained in FIG. 1. Thus, even if the stapling process is set when the job is started, when the operation is the size-mixing job or when the input number of sheets exceeds the maximum number of sheets that can be stapled, the printing can be executed after canceling the stapling process.
In the above-described prior art, under the control of determining whether the stapling process can be executed or not in the completion type, the received document images cannot be sequentially printed, and thus the processing capacity is made low.
However, if the received document images are sequentially printed to improve the processing capacity, it cannot be determined in advance whether the stapling process can be executed or not, in the case of the size-mixing job where the image data of different sizes is mixed, and therefore, an appropriate operation cannot be executed.